This invention relates to a process for reducing residual organic chloride species in phenylchlorosilanes. In the described process, a crude mixture comprising phenylchlorosilanes, organic chlorides, and a phenyl source are contacted with a Lewis acid forming material. The organic portion of the organic chlorides forms hydrocarbon adducts with the phenyl source. The hydrocarbon adducts can then be more easily separated from the phenylchlorosilanes.
Phenylchlorosilanes can be produced, for example, by a Grignard type reaction between chlorobenzene and methyltrichlorosilane methyltrichlorosilane. The result of this reaction is a crude mixture containing phenylchlorosilanes and a whole spectrum of chlorinated hydrocarbons and phenyl containing impurities. The organic chlorides, in many cases, have boiling points near those of the desired phenylchlorosilanes and can not be separated by the commonly used practice of distillation.
As impurities in the phenyhlchorosilanes, organic chlorides can serve as a latent sources of ionic chloride. This ionic chloride can create stability problems in hydrolysis intermediated formed from the phenylchlorosilanes. This problem has been found to exist even when the organic chlorides are present at parts per million in the phenylchlorosilane precursors to these hydrolysis intermediates. Therefore, a process which is effective at reducing organic chloride, even at these low levels, is desirable.
McEntee, U.S. Pat. No. 4,127,598, issued Nov. 28, 1978, describes a process for removing chlorinated biphenyls from impure phenylchlorosilanes with an absorbent bed. The adsorbent bed is selected from a class consisting of a molecular sieve bed and a charcoal bed.
Motomiya, Japanese patent publication No. 50-39649, published Dec.18, 1975, describes a method for separating olefinic compounds and saturated compounds having a branching tertiary carbon from crude organohalosilanes. The described process is described as selectively polymerizing the hydrocarbon compounds when they are contacted with a Lewis acid or a metal hydroxide which can become a Lewis acid. The polymerized hydrocarbon compounds are separated from the organhalosilanes by distillation. The presence or removal of organic chlorides is not discussed by Motomiya.
Marko, et al., U.S. PAT. No. 4,774,347, issued Sept. 27, 1988, describes a process for reducing the chlorocarbon content of alkylsilanes. The described process comprises contacting crude alkylsilanes, containing as a minor portion chlorocarbons, and a hydrogen-containing silane with a catalyst. The catalyst is described as a Lewis acid forming material. In the described process, the chloride of the chlorocarbon is exchanged for a hydrogen atom of the hydrogen-containing silane to form a saturated hydrocarbon which may or may not be separated from the desired alkysilanes. This chemistry is not operative with the chlorine containing impurities found in phenylchlorosilanes.